For the first time in 35 years, Wisconsin Republicans are gearing up for a divisive primary in the 6th District.

GOP Rep. Tom Petri's retirement announcement last week has made the district more competitive, but Republicans are expected to hold the seat. (The Rothenberg Political Report/Roll Call rates this race as a Safe Republican contest .)

Two Republicans have thrown their hats into the ring so far.

Before Petri announced his departure, state Sen. Glenn Grothman joined the race , describing the congressman as not sufficiently conservative. Grothman sent out a fundraising letter Monday, signaling he's gearing up for the race.

State Rep. Duey Stroebel said this weekend that he also plans to run, and he has hired top Wisconsin strategist Darrin Schmitz.

State Sen. Joe Leibham is also considering a bid and plans to make a decision in the coming days. Some Wisconsin strategists speculated that Leibham would be a front-runner in the GOP primary because his legislative terrain encompasses much of the 6th District.

Another potential Republican candidate is John Hiller, an adviser to Gov. Scott Walker.

Wisconsin Republicans also said state Senate Majority Leader Scott Fitzgerald could run, but Fitzgerald said Monday that he would not join the race.

Fitzgerald’s decision “opens up a whole range of opportunities for other people,” said Scott Becher, a Republican consultant from Wisconsin. But he added that candidates face “a tight time frame to get your name out there” with a June filing deadline and an August primary.

“From where they stand on the issues, I think everybody’s going to be similarly situated,” said Mark Graul, a Wisconsin GOP strategist, who added, “a lot will come down to who can raise the most resources.”

A heated Republican primary could help Democrats, who are hoping to attract the district’s moderate voters to pick up the seat.

“For Democrats to take back the House this is exactly the district we have to win,” said Democratic political consultant Eric Hogensen.

But the seat is a long shot for Democrats. Mitt Romney carried the district with 53 percent in 2012.

No Democrats have announced they are running yet, but party operatives said potential candidates include Manitowoc Mayor Justin Nickels, Winnebago County Executive Mark Harris and former state Sen. Jessica King.

According to Bob Schweder, the 6th District’s Democratic chairman, this race is “probably the best shot we’ve had in 30 years,” He added, however, “It’s still going to be a tough uphill battle.”